Automatic choke



Oct. 16, 1962 A. s. LUCAS 3,058,727

AUTOMATIC CHOKE Filed June 26. 1959 v 3 Sheets-Sheet 1 INVENTOR. 4Lw/v6T 10643 E- 5 MQML ATTDE/VE) Oct. 16, 1962 A. s. LUCAS 3,058,727

AUTOMATIC CHOKE Filed June 26, 1959 3 SheetsSheet 2 IN VEN TOR. 41 WM 51 00 45 ATTQENE) Uite States atent 3,958,727 AUTOMATIC CHOKE Alvin S.Lucas, Farmington, Mich, assignor to Holley Carburetor Company, VanDyke, Mich, a corporation of Michigan Filed June 26, 1959, Ser. No.823,213 11 Claims. (El. 261-39) This invention relates generally tocarburetors or other fuel controls for internal combustion engines, andmore particularly to means for automatically operating the chokingmechanism provided therein.

Most carburetors of present design include a thermostatic element forcontrolling the amount of choke opening according to temperature.Additionally, many choke control devices employ a manifold vacuumresponsive piston for initially opening the choke a predetermined degreewhen the cold engine starts and becomes self-sustaining.

Although this general arrangement has been accepted commercially,certain inherent characteristics thereof sometimes cause undesirableresults. Some of these results are improper choke come-cit and come-ontimes, the come-off time being that time required to fully open thechoke after the cold engine is started and the come-on time being thattime required to close the choke after a substantially warmed engine isshut down.

Accordingly, this invention is directly concerned with the aboveproblems and has as its broad purpose the objective of providing means,in a temperature responsive choke control mechanism, for controlling thechoke corneoff and come-on times.

Other more specific objects and advantages will become apparent whenreference is made to the following description and accompanyingillustrations wherein:

FIGURE 1 is a perspective view illustrating generally a carburetorembodying the invention, with the carburetor being mounted on an engine.

FIGURE 2 is a fragmentary perspective exploded view illustrating thedetails of construction of the lefthand portion of FIGURE 1.

FIGURE 3 is an enlarged, fragmentary sectional view illustrating ingreater detail the piston and associated elements shown by FIGURE 2.

FIGURE 4 is a cross-sectional View taken on the plane of line 44 ofFIGURE 3, and looking in the direction of the arrows.

FIGURE 5 is a graph comparing the operation of a choke mechanismembodying the invention with that of presently used choke mechanisms notembodying the invention.

FIGURE 6 is a view similar to FIGURE 3, but illustrating a modificationof the invention.

FIGURE 7 is a cross-sectional view taken on the plane of line 7--7 ofFIGURE 6 and looking in the direction of the arrows.

Referring to the drawings in greater detail, FIGURE 1 illustrates acarburetor 10 having a throttle body 12, an air intake 14 with inductionpassages therethrough adapted to be controlled by a choke valve 16,which is operatively connected by means of arms 18 and 20 and link 22 tothe automatic choke control 24. The carburetor is shown mounted on theintake manifold, a portion of which is illustrated at 25.

FIGURE 2 illustrates a housing 26, suitably secured as by screws 28 tothe carburetor 10 and having a cylinder 30 formed therein containing apiston 32 which is connected through a linkage 34 to the choke lever 36.A shaft 38, extending through and rotatable in one wall of the housing26 has secured to it at one end thereof a choke lever 36, and at theother end thereof a lever 20 (FIGURE I). The choke lever 36 has anoutwardly extending projecice tion 49 which is adapted to coact with thefree outer end &2 of thermostatic element 44- through an arcuate opening46 in the housing cover plate 48.

The thermostatic housing 51 has a centrally located shaft rigidlysecured therein to which the inner end of the thermostatic element 44 issecured. Any suitable means such as the clamping ring 52 may be employedto hold the cover plate 43 and housing 56} in alignment with and againstthe housing 26. The ring 52 may be secured by means of screws 54 and thecooperating threaded portions 56.

(Ionduit 53 communicates 'between a source of heated air, such as thestove 59, and the chamber formed by the cover plate 43 and housing 56'.Its purpose is to deliver a controlled amount of air, which is at atemperature indicative of engine temperature, to the thermostaticelement 44 in order that the element 44 may react to it and influencethe position of the choke valve 16 accordingly. The general path of thisheated air is indicated by the arrows in FIGURE 2, its ultimate exitbeing to the intake manifold through a porting means between the piston32 and the walls of the cylinder 30; the latter is to be described morefully in connection with FIGURE 3.

Conduit 69 communicates generally between the cylinder 3G and a sourceof engine manifold vacuum in such a manner as to cause movement of thepiston 32 in a direction resulting in a clockwise rotation of lever 36,and at the same time to draw the heated air referred to above throughconduit 5%.

The construction described above is well known to those skilled in theart as the standard automatic choke employed on most carburetors. Otherfeatures, such as a fast idle mechanism, are normally associatedtherewith, but they need not be described since they form no part of theinvention.

Referring now to FIGURE 3, piston 32 has a cavity 66 formed thereinwhich is adapted to receive the linkage 34. The other end of the pistonis closed and is subjected to manifold pressures as previouslydescribed. One end of the linkage 34 may be secured to the piston 32 byany suitable means such as pin 62; the other end of linkage 34 has aslot 35 therein which is adapted to slidably receive a pin 64 which issecured to the lever 36. The slots 68, which constitute the portingmeans already referred to above, may be formed in the wall of cylinder30.

A thermostatic assembly '70, as illustrated in FIGURE 4, serves tocontrol a vent 72 adapted to communicate with the atmosphere. Theassembly 76' is comprised generally of a thermostatic element 74-secured at one end to a mounting member 76 as by a rivet 78. Themounting member may of course be secured to the housing 26 in anysuitable manner, or alternatively be formed as an integral portion ofthe housing 26. The free end of the thermostatic element 74 has a valvemember 89 operatively connected thereto and positioned in such a mannerso as to be capable of controlling the flow of air through vent 72. Therelative positions of vent 72 and valve '80 may be of course, adjustedby inserting any suitable tool into the slot 73 and turning the bodyportion of vent 72 so as to raise or lower it.

Operation of Invention Assuming for the purpose of illustration that theengine is cold and is being cranked, the thermostatic element 44 may bein its unwound condition, thereby causing its end 42 to positionprojection 40 of lever 36 in its extreme counter-clockwise position. Thelever 36, being secured to shaft 38, rotates the shaft and arm 20 whichis secured to it counter-clockwise to cause the choke valve 116 toassume a position which substantially closes on the flow of air throughthe carburetor induction passage 14. All

I 3 of these elements will continue to occupy these respective positionswhile the engine is being cranked.

As soon as the engine tires and becomes self-sustaining, manifold vacuumrises to a value sufiicient to move the vacuum piston 32 downwardly inopposition to the force of thermostat 44. The extent of movement of thispiston is determined by the position of the porting means, that is,slots 68 within the cylinder 30.

As soon as the piston 32 uncovers the ends of the slots 68, the eifectof the manifold vacuum on the piston is reduced to such a degree thatthe piston is unable to further overcome the opposing force of thethermostat 44. As the engine continues to run, air is drawn from anysuitable stove '59 through conduits 58, 82, and 84, throughorifice 86 incover plate 48, and into the chamber formed by the housing '50 and coverplate 48. This air warms the thermostat 44 and passes through thearcuate opening 46 Within the cover plate. The air is then drawn throughthe slots 68 in cylinder 30. Ultimately, the air is drawn throughorifice 88 into conduit 90 leading from the cylinder to conduits 92 and60, which are in turn connected to a source of manifold vacuum.

After the piston has performed its function of opening the choke '16 apredetermined degree, the thermostatic element 44 is then required tocontrol the choke position until it has been fully opened. One of themost serious defects of this arrangement, which till this point of thediscussion is common to those choke mechanisms currently used, is thatthe come-off time is excessive. At-

' temps to correct this defect by the substitution of a higher ratethermostatic element failed because the combustible mixture supplied bythe carburetor during the period that the choke was progressivelyopening was made overly lean.

The invention, in order to correct these problems of improper come-offand come-on times, provides means such as illustrated by thethermostatic assembly 70 for varying the responsiveness of thethermostat 44.

The graph of FIGURE 5 illustrates three separate curves A, B, and C ofchoke valve position in relation to time. Of course, the choke valveposition corresponds to the position assumed by the free end 42 of thethermostat 44 until it is fully opened, after which the end 42 continuesto move some amount away from the projection of arm .36. The points Yand Z illustrate such overtravel by the free end 42.

Referring again to FIGURE 4, let it be assumed, for purposes ofillustration, that the engine on which the carburetor is to be used hasthe characteristic which requires that the choke valve 16 be at a pointP at some time X after the engine is started. In order to accomplishthis, a thermostat 44 is provided whichwill have a particular ratewhereby the performance slope passes through points M and P. When thisis done, however, the come-off time, as determined at point N, isexcessive; this causes overly rich combustible mixtures and pooreconomy.

Realizing that the desired come-off time is at some point R, athermostatic element of higher rate could be used so as to have a slopepassing through points M and R. With this change, however, it is to benoted that for the same time X the choke 16 will have assumed a morenearly open position S, than it had previously at point P. In otherwords, with such a change the come-off time would be proper but thecombustible mixture supplied as a consequence of choke position would betoo lean for proper engine operation during the warm-up period.

In contrast to the curves A and C, the invention pro-' vides meanswhereby the performance curve of a particular thermostat having adefinite rate can be controlled so as to deliver the proper richness ofthe combustible mixture and yet attain the desired come-off time. Such acurve is illustrated at B in FIGURE 5.

The method by which the invention accomplishes this is by the use of thethermostatic assembly 70. That is,

as the engine is started cold, the valve 8t) is held away from the port72 by means of thermostatic element 74.

As a result of this, the vacuum which exists generally Within thechamber 26 as described previously causes 5 some unheated atmosphericair to be drawn in instead of all heated air through the conduit 58. Bysuch means the heating effect upon the thermostat 44- is minimizedgenerally during the time X.

As the thermostatic element 74 becomes heated, the port 72 isprogressively closed causing less unheated atmospheric air to be drawnin and conversely more heated air to be supplied to the thermostat 44.In this manner, the performance curve can be shaped so as to passthrough the desired points M, P, and R.

Additionally, an added feature of this invention is that the come-ontime can be prolonged. That is, the present choke mechanisms are tooquick in the responsiveness after the engine is shutdown. This usuallyoccurs as a result of the use of low rate thermostats which when exposedto the full heat of the warmed engine have only a slight movement awayfrom the lever 40, as illustrated by the position of point Z on theordinate scale.

By the use of .a high rate thermostat 44 in the invention, a point Y canbe attained which is substantially increased ordinate-Wise over thepoint Z. As a result of this, the engine has to cool to a greaterdegree, which in turn requires a longer period of time, before the choke16 will again begin to close. This feature again improves the economy.

A modification of this invention, as illustrated in FIG- URE 6, employsmechanical means for controlling the amount of unheated bleed airinstead of the thermostatic means disclosed in FIGURES 2, 3 and 4. Allof the elements in FIGURE 6 which are identical or similar to those ofthe prior figures are identified with primed numerals. 1

In this embodiment, a spring 94 having a valving member 96 secured toone end of it is mounted on the housing 26' by any suitable means suchas a block 93. The spring 94 may be secured to the block 98 in anysuitable manner such as by a rivet 100. The arm portion 37 of lever 36'has a projecting member 102 which is adapted to be in continuous contactwith the spring 94.

FIGURE 7 illustrates a typical coaction of the various elements of themodification. Referring more specifically to FIGURE 7, it can be seenthat the spring 94 is formed so as to present a generally inclined camsurface 104 to member 1102-, so that as the member 102 traverses alongthe length of the spring the valving member 96 is progressively andcontinuously brought closer to the bleed jet 72.

The movement of the lever 36' is again a function of the choke plate 16position. Since the choke plate posi- .tion is an indication of thetemperature of thermostat 44, it might be stated broadly that thismechanical embodiment is again indicative of'engine temperature. As 7 Ithe valving member 96 approaches the bleed jet 72, the

' amount of cold air drawn into housing 26' by virtue of themanifoldflvacuum existing therein is reduced. As the quantity of coldair is reduced, the quantity of heated air is consequently increased soas to cause a more rapid heating of the thermostat 44. The end result ofthis modification is the same as that illustrated in the previousfigures in that the come-off and come-on times plus the fuel-air ratioduring theinterim periods can be controlled by the shape and position ofthe mechanical spring 94.

Although only two embodiments of the invention have been disclosed anddescribed, it is apparent that other 7|) modifications of the inventionare possible Within the scope of the appended claims.

What I claim as my invention is: 1 In a carburetor for van'internalcombustion engine having an induction passage and a choke valvecontrolling the flow of air therethrough, a housing, a thermostaticelement in said housing operatively connected to said choke valve forregulating the opening and closing of said choke valve in accordancewith engine temperature, means including an inlet in said housing fordirecting a flow of heated fluid to said thermostatic element, and meansfor reducing the temperature of said fluid flow passing through saidinlet until a predetermined temperature is attained.

2. In a carburetor for an internal combustion engine having an inductionpassage and a choke valve controlling the fiow of air therethrough, afirst thermostatic element operatively connected to said choke valve forregulating the opening and closing of said choke valve in accordancewith engine temperature, and additional thermostatic means for delayingthe full application of engine heat to said first thermostatic elementuntil a predetermined engine temperature is attained.

3. In a carburetor for an internal combustion engine having an inductionpassage and a choke valve controlling the flow of air therethrough, ahousing, a thermostatic element in said housing operatively connected tosaid choke valve for regulating the opening and closing of said chokevalve in accordance with engine temperature, and means for admittingcold ambient air into said housing in decreasing quantities as thetemperature of said engine increases.

4. In a carburetor for an internal combustion engine having an inductionpassage and a choke valve controlling the flow of air therethrough, asource of engine heat, a thermostatic element operatively connected tosaid choke valve for regulating the opening and closing of said chokevalve, means for continually directing said engine heat to saidthermostatic element so as to cause said thermostatic element to reactgenerally in accordance with engine temperature, and separate mechanicalmeans for reducing the degree of said engine heat supplied to saidthermostatic element until said engine attains a predeterminedtemperature.

5. In a carburetor for an internal combustion engine having an inductionpassage and a choke valve controlling the flow of air therethrough, ahousing, a source of engine heat, a thermostatic element containedwithin said housing and operatively connected to said choke valve forregulating the opening and closing of said choke valve, means fordirecting said engine heat to said thermostatic element so as to causesaid thermostatic element to react generally in accordance with enginetemperature, and separate mechanical valve means for reducing the supplyof said engine heat to said thermostatic element by admitting coldambient air into said housing until said choke valve attains apredetermined degree of opening.

6. The method of controlling the richness of the combustible mixturedelivered to an internal combustion engine having a carburetor with aninduction passage and a choke valve in said induction passage adapted tobe controlled by a thermostatic element responsive to the heat generatedby said engine, the steps comprising the method being first, minimizingthe degree of said heat applied to said thermostatic element by theaddition of cold ambient air until a first predetermined enginetemperature is attained; second, increasing the degree of said heatapplied to said thermostatic element by reducing the quantity of coldambient air after said first predetermined temperature is attained anduntil a second predetermined engine temperature is reached; and last,eliminating all cold ambient air and applying all of said heat to saidthermostatic element after said second predetermined engine temperatureis attained.

7. In a carburetor having a choke valve therein, an automatic chokecontrol device comprising, a choke shaft secured to said valve, a membersecured to said shaft and adapted to be rotated therewith, a housing, asecond shaft mounted through one side of said housing and adapted to berotated therein, an arm secured to one end of said second shaftexternally of said housing so as' to be rotatable therewith, meansconnecting said member with said arm, a cylinder open at one end andsubstantially closed at its other end, a piston in said cylinder, 9.second arm having a projection thereon secured to the other end of saidsecond shaft within said housing adapted to rotate said second shaft,conduit means leading from the space between the said piston and theclosed end of said cylinder and communicating with a source of enginesuction, second'conduit means leading from the said housing andcommunicating with a source of heated air at substantially atmosphericpressure, thermostatic means Within said housing adapted to bias saidprojection in a direction so as to close said choke valve, connectingmeans between said second arm and said piston enabling said piston tooppose the movement of said thermostat whenever said engine is running,cam operated valve means adapted to at times communicate between theatmosphere and the interior of said housing, and means secured to saidsecond arm for actuating said cam operated valve means in accordancewith the position of said second arm member.

8. In a carburetor for an internal combustion engine having an inductionpassage with a choke valve therein, an automatic choke control devicecomprising, a choke shaft secured to said valve, a member secured tosaid shaft and adapted to be rotated therewith, a housing, a secondshaft mounted through one side of said housing and adapted to be rotatedtherein, an arm secured to one end of said second shaft externally ofsaid housing so as to be rotatable therewith, means connecting saidmember. with said arm, a cylinder open at one end and substantiallyclosed at its other end, a piston in said cylinder, a second arm havinga projection thereon secured to the other end of said second shaftwithin said housing adapted to rotate said second shaft, conduit meansleading from the space between the said piston and the closed end ofsaid cylinder and communicating With a source of engine suction, secondconduit means leading from the said housing and communicating with asource of heated air at substantially atmospheric pressure, firstthermostatic means Within said housing adapted to bias said projectionin a direction so as to close said choke valve, connecting means betweensaid second arm and said piston enabling said piston to oppose themovement of said thermostat whenever said engine is running, valve meansadapted to at times communicate between the atmosphere and the interiorof said housing, and second thermostatic means for actuating said valvemeans in accordance with the temperature of said engine.

9. The method of controlling the richness of the combustible mixturedelivered to an internal combustion engine having a carburetor with aninduction passage and a choke valve in said induction passage adapted tobe controlled by a thermostatic element responsive to the heat generatedby said engine, the steps comprising the method being first, minimizingthe degree of said heat applied to said thermostatic element by theaddition of cold ambient air at low engine temperatures; second,progressively increasing the degree of said heat applied to saidthermostatic element by progressively reducing the quantity of said coldambient air as engine temperature increases and until a predeterminedhigher engine temperature is reached; and last, eliminating all of saidcold ambient air and applying all of said heat to said thermostaticelement after said predetermined higher engine temperature is attained.

10. In a carburetor for an internal combustion engine having aninduction passage and a choke valve controlling the flow of airtherethrough, a housing, a thermostatic element in said housing operablyconnected to said choke valve for resisting the opening of said chokevalve with decreasing force as engine temperature increases, meansincluding an inlet to said housing for directing a flow of heated fluidindicative of engine temperature to said thermostatic element, and meansresponsive to the temperature of said fiuidfor introducing decreasingamounts of cold ambient air as the temperature of said fluid increases.

11. In a carburetor for an internal combustion engine having aninduction passage and a choke valve controlling the flow of airtherethrough, a housing, a thermostatic element in said housing operablyconnected to said choke valve for resisting the opening of said chokevalve with decreasing force when engine temperature increases, meansincluding an inlet to said housing for directing a flow of heated fluidindicative of engine temperature to said thermostatic element, and meansresponsive to the position of said choke valve for introducingdecreasing amounts of cold ambient air as said choke valve moves to amore fu'lly opened position.

1 References Cited in the file of this patent UNITED STATES PATENTS2,698,168 Olson Dec. 28, 1954 2,719,706 Winkler Oct. 4, 1955 2,803,442Hausburg Aug. 20, 1957 2,848,201 Bennett Aug. 19, 1958 2,937,635 Carlsonet a1 May 24, 1960 2,942,596 Carlson June 28, 1960

